Abstract
This study addressed the effects of recycled polyethylene (RPE) on the performances of both asphalt binders and asphalt mixtures. Whether using a RPE in an asphalt mixture might leach harmful chemicals into rainwater or melted snow during the pavement service life was also determined. Two processes, wet and dry, were used to formulate the RPE modified asphalt binders and mixtures. In the wet process, RPE is added to asphalt binder. In the dry process, it is added to heated aggregates. Two RPE from two sources and two PG 64 -22 virgin asphalt binders from two sources were used in this study. Additionally, the impact of using recycled polyethylene (RPE) on the predicted rutting and bottom-up fatigue cracking of RPE modified asphalt pavement sections and on the return on investment (ROI) was evaluated. The AASHTOWare Pavement Mechanistic-Empirical Design (PMED) was used to predict rutting and bottom-up fatigue cracking. Life-cycle cost analyses (LCCA) using Federal Highway Administration (FHWA) RealCost Software were used to analyze the return on investment (ROI). Three Superpave 12.5-mm mixtures were evaluated: one control and two RPE modified mixtures designed using wet and dry processes. To increase the prediction accuracies, local laboratory-derived calibration coefficients were used in AASHTOWare PMED based on the repeated load permanent deformation test (RLPDT) and flexural bending beam fatigue tests. Using time versus asphalt concrete rutting and bottom-up fatigue cracking charts, the service life for initial construction and subsequent future pavement rehabilitation/preservation activities were determined for each pavement section. The ROI was then evaluated using a 30-year analysis period. In conclusion, RPE improved the rutting resistances of the asphalt binders and asphalt mixtures. However, it had adverse effects on their resistances to intermediate-temperature and non-load associated cracking. The dry process could produce a mixture with a higher RPE dosage compared to the wet process using one virgin asphalt binder but not using the other; thus, virgin asphalt binder source was a significant factor for the dry process. Based on an embryotoxicity test, RPE can be used by asphalt paving industry without having any significant environmental risks. Regarding the LCCA, the most cost-effective pavement over the 30-year analysis period was provided by the pavement section produced using the dry process followed by the wet process while the least cost-effective pavement was the control pavement section. Hence, the study presented beneficially contributed to the current state-of-the-practice by presenting how recycled plastics impact performances of both asphalt binders and mixtures, predicted rutting and bottom-up fatigue cracking performances, and the return on investment (ROI) when using both wet and dry mixing processes.